Internal mix spray nozzle assemblies are known that utilize pressurized air for breaking down liquid into relatively small size particles. Such spray nozzle assemblies have particular utility in gas scrubbing applications, such as where lime slurry or the like is atomized and sprayed into a discharging stream of combustion gases for removing sulfur dioxide or other combustion byproducts. For efficient combustion gas scrubbing, it is necessary that the slurry be atomized into a very fine liquid particle spray.
Such spray nozzle assemblies commonly direct the finely atomized liquid from a plurality of circumferentially spaced discharge orifices of an air cap of the nozzle so as to generate an outwardly expanding conical spray pattern. During operation, fine particles of the high pressure discharging flow streams from the plurality of discharge orifices can migrate inwardly back toward the nozzle and create a heavy buildup of particulate matter about the discharge orifices that choke off the spray and significantly degrade performance. This creates the need for frequent costly cleaning of the air cap of such buildup.
To minimize such build up, it is known to form the discharge orifices of the air cap at compound angles to the axis of the spray nozzle so as to impart a tangential like swirling action of the discharging sprays. However, the increased surface areas of such angled discharge orifices can be subject to substantial wear in only a few days, as depicted in FIG. 7 by the wear “w” in the discharge orifices of an air cap of a prior art spray nozzle assembly, necessitating costly field repair or replacement.